Process for hydrotreatment and hydroisomerization of feedstocks obtained from a renewable source implementing a modified zeolite

ABSTRACT

This invention describes a process for treatment of feedstocks obtained from a renewable source implementing a catalyst that comprises at least one hydro-dehydrogenating metal that is selected from the group that is formed by the metals of group VIB and group VIII of the periodic table and a substrate that comprises at least one zeolite that has at least one series of channels whose opening is defined by a ring with 8 oxygen atoms modified by a) at least one stage for introducing at least one alkaline cation that belongs to group IA or IIA of the periodic table, b) a stage for treating said zeolite in the presence of at least one molecular compound that contains at least one silicon atom, c) at least one stage of partial exchange of said alkaline cations by NH 4   +  cations, and d) at least one heat treatment stage.

FIELD OF THE INVENTION

In an international context marked by the rapid growth of fuelrequirements, in particular gas oil and kerosene bases in the EuropeanCommunity, the search for new sources of renewable energy that can beintegrated into the traditional arrangement of the refining andproduction of fuels constitutes a major venture.

In this regard, there has been a very sharp resurgence, in recent years,of interest in integration into the process for refining new products ofplant origin, obtained from the conversion of the lignocellulosicbiomass or obtained from the production of vegetable oils or animalfats, due to the increase in the cost of fossil fuels. Likewise, thetraditional biofuels (ethanol or methyl esters of vegetable oils,primarily) have acquired an actual status of a supplement topetroleum-type fuels in the fuel pools. In addition, the processes thatare now known that use vegetable oils or animal fats are at the originof CO₂ emissions, known for these negative effects on the environment. Abetter use of these bio resources, such as, for example, theirintegration into the fuel pool, would therefore offer a certainadvantage.

The high demand for gas oil and kerosene fuels, coupled with theimportance of concerns linked to the environment, reinforces theadvantage of using feedstocks obtained from renewable sources. Amongthese feedstocks, it is possible to cite, for example, vegetable oils,animal fats that are raw or that have been pretreated, as well asmixtures of such feedstocks. These feedstocks contain chemicalstructures such as triglycerides or esters or fatty acids, whereby thestructure and the length of the hydrocarbon chain of the latter arecompatible with the hydrocarbons that are present in the gas oils andkerosene.

One possible method is the catalytic transformation of the feedstockthat is obtained from the renewable source of paraffinic fuel from whichoxygen is removed in the presence of hydrogen (hydrotreatment). Numerousmetal or sulfur catalysts are known for being active for this type ofreaction.

These processes for hydrotreatment of the feedstock obtained from arenewable source are already well known and are described in numerouspatents. It is possible to cite, for example, the patents: U.S. Pat. No.4,992,605, U.S. Pat. No. 5,705,722, EP 1,681,337 and EP 1,741,768.

The use of solids based on transition metal sulfides makes possible theproduction of paraffins from the ester-type molecule according to tworeaction methods:

-   -   The hydrodeoxygenation leading to the formation of water by        consumption of hydrogen and to the formation of hydrocarbons of        the carbon number (Cn) that is equal to that of the starting        fatty acid chains,    -   The decarboxylation/decarbonylation leading to the formation of        carbon oxides (carbon monoxide and carbon dioxide: CO and CO2)        and to the formation of hydrocarbons, having one carbon less        (Cn-1) relative to the starting fatty acid chains.

The liquid effluent that is obtained from these hydrotreatment processesessentially consists of n-paraffins that can be incorporated in the gasoil and kerosene pool. So as to improve the properties under coldconditions of this hydrotreated liquid effluent, a hydroisomerizationstage is necessary for transforming the n-paraffins into branchedparaffins exhibiting better properties under cold conditions.

The patent application EP 1 741 768 describes, for example, a processthat comprises hydrotreatment followed by a hydroisomerization stage soas to improve the properties under cold conditions of the linearparaffins that are obtained. The catalysts that are used in thehydroisomerization stage are bifunctional catalysts [and] consist of ametal active phase that comprises a metal of group VIII that is selectedfrom among palladium, platinum and nickel, dispersed on a molecularsieve-type acid substrate that is selected from among SAPO-11, SAPO-41,ZSM-22, ferrierite or ZSM-23, whereby said process operates at atemperature of between 200 and 500° C., and at a pressure of between 2and 15 MPa. Nevertheless, the use of this type of solid brings about aloss in yield of middle distillates.

The research work carried out by the applicant on the modification ofnumerous zeolites and crystallized microporous solids and on thehydrogenating active phases has led to the discovery that, surprisinglyenough, a catalyst for hydroisomerization of paraffinic hydrocarbonfeedstocks and in particular obtained from the hydrotreatment offeedstocks obtained from a renewable source, comprising an active phasethat contains at least one hydro-dehydrogenating element that isselected from among the elements of group VIB and group VIII, and asubstrate that comprises at least one zeolite that exhibits at least oneseries of channels whose opening is defined by a ring with 8 oxygenatoms, whereby said zeolite is modified by a particular modificationprocess, made it possible to obtain a higher activity, i.e., a higherlevel of conversion, while making it possible to obtain an improvedyield of middle distillates (jet fuels and gas oils), thehydroisomerization stage being implemented in a process for treatment offeedstocks obtained from a renewable source comprising a hydrotreatmentstage upstream from said hydroisomerization stage.

The modification of zeolite by deposition of compounds containing atleast one molecular compound containing at least one silicon atom hasbeen very widely studied in the past. Moreover, it is possible to citethe patent U.S. Pat. No. 4,402,867 that describes a method forpreparation of a zeolite-based catalyst that comprises a stageconsisting in depositing, in aqueous phase, at least 0.3% by weight ofamorphous silica inside the pores of the zeolite. The patent U.S. Pat.No. 4,996,034 describes a process for substitution of aluminum atomsthat are present in a zeolitic framework by silicon atoms, whereby saidprocess is carried out in one stage in aqueous medium usingfluorosilicate salts. The patent U.S. Pat. No. 4,451,572 describes thepreparation of a zeolitic catalyst that comprises a stage for depositionof organosilicic materials in vapor phase or in liquid phase, wherebythe targeted zeolites are zeolites with wide pores, in particular the Yzeolite.

One objective of the invention is therefore to provide a process fortreatment of feedstocks obtained from a renewable source implementing—inone hydroisomerization stage downstream from a hydrotreatment stage—ahydroisomerization catalyst that comprises a modified zeolite-basedsubstrate that makes it possible to obtain high yields of gas oil andkerosene bases.

Another objective of the invention is to provide a process for treatmentof feedstocks obtained from a renewable source implementing—in onehydroisomerization stage downstream from a hydrotreatment stage—acatalyst that comprises as substrate a modified zeolite that makes itpossible to reduce the 150° C. light fraction production.

OBJECT OF THE INVENTION

More specifically, the invention relates to a process for treatment offeedstocks obtained from a renewable source and comprising the followingstages:

a) Hydrotreatment of said feedstock in the presence of a fixed-bedcatalyst that comprises a hydro-dehydrogenating function comprising atleast one metal of group VIII and/or group VIB, taken by itself or in amixture, and a substrate that is selected from the group that is formedby alumina, silica, silica-aluminas, magnesia, clays and mixtures of atleast two of these minerals, whereby said hydrotreatment stage operatesat a temperature of between 200 and 450° C., at a pressure of between 1MPa and 10 MPa, at an hourly volumetric flow rate of between 0.1 h⁻¹ and10 h⁻¹, and in the presence of a total quantity of hydrogen mixed withthe feedstock such that the hydrogen/feedstock ratio is between 70 and1,000 Nm³ of hydrogen/m³ of feedstock,

b) Separation, starting from the effluent that is obtained from stagea), of hydrogen, gases, and at least one hydrocarbon base,

c) Hydroisomerization of at least a portion of said hydrocarbon basethat is obtained from stage b) in the presence of a fixed-bedhydroisomerization catalyst, whereby said catalyst comprises at leastone hydro-dehydrogenating metal that is selected from the group that isformed by the metals of group VIB and group VIII of the periodic table,taken by itself or in a mixture, and a substrate that comprises at leastone zeolite that has at least one series of channels whose opening isdefined by a ring with 8 oxygen atoms, modified by a′) at least onestage for introducing at least one alkaline cation that belongs to groupIA or IIA of the periodic table, b′) a stage for treatment of saidzeolite in the presence of at least one molecular compound that containsat least one silicon atom, c′) at least one stage of partial exchange ofsaid alkaline cations by NH₄ ⁺ cations, and d′) at least one heattreatment stage, whereby said hydroisomerization stage is carried out ata temperature of between 150 and 500° C., at a pressure of between 1 MPaand 10 MPa, at an hourly volumetric flow rate of between 0.1 and 10 h⁻¹,and in the presence of a total quantity of hydrogen mixed with thefeedstock such that the hydrogen/feedstock ratio is between 70 and 1,000Nm³/m³ of feedstock,

d) Separation, starting from the effluent that is obtained from stagec), of hydrogen, gases, and at least one gas oil base and one kerosenebase.

DETAILED DESCRIPTION OF THE INVENTION

This invention is particularly devoted to the preparation of gas oil andkerosene fuel bases corresponding to new environmental standards,starting from feedstocks obtained from renewable sources.

The feedstocks that are obtained from renewable sources used in thisinvention are advantageously selected from among the oils and fats ofplant or animal origin, or mixtures of such feedstocks, containingtriglycerides and/or free fatty acids and/or esters. The vegetable oilscan advantageously be raw or refined, totally or partially, and obtainedfrom the following plants: canola, sunflower, soybean, palm,palm-kernel, olive, coconut, and jatropha, whereby this list is notexhaustive. The oils of algae or fish are also relevant. Animal fats areadvantageously selected from among lard or fats composed of waste fromthe food industry or obtained from catering industries.

These feedstocks essentially contain chemical structures of thetriglyceride type that one skilled in the art also knows under the namefatty acid triesters as well as free fatty acids. A fatty acid triesteris thus composed of three chains of fatty acids. These fatty acid chainsin triester form or in free fatty acid form have a number ofunsaturations per chain, also called a number of carbon-carbon doublebonds per chain, generally encompassed between 0 and 3 but that can behigher in particular for the oils that are obtained from algae thatgenerally have a number of unsaturations per chain of 5 to 6.

The molecules that are present in the feedstocks that are obtained fromrenewable sources used in this invention therefore have a number ofunsaturations, expressed per triglyceride molecule, advantageouslybetween 0 and 18. In these feedstocks, the unsaturation level, expressedby number of unsaturations per hydrocarbon fatty chain, isadvantageously between 0 and 6.

The feedstocks that are obtained from renewable sources generally alsocomprise various impurities and in particular heteroatoms such asnitrogen. The nitrogen contents in the vegetable oils are generallybetween approximately 1 ppm and 100 ppm by weight according to theirnature. They can reach up to 1% by weight in particular feedstocks.

Prior to stage a) of the process according to the invention, thefeedstock can advantageously undergo a stage for pretreatment orpre-refining so as to eliminate, by a suitable treatment, contaminantssuch as metals, like the alkaline compounds, for example, onion-exchange resins, alkaline-earths, and phosphorus. Suitabletreatments can be, for example, heat treatments and/or chemicaltreatments that are well known to one skilled in the art.

According to stage a) of the process according to the invention, thefeedstock, optionally pretreated, is brought into contact with afixed-bed catalyst comprising a hydro-dehydrogenating function thatcomprises at least one metal of group VIII and/or group VIB, taken byitself or in a mixture and a substrate that is selected from the groupthat is formed by alumina, silica, silica-aluminas, magnesia, clays andmixtures of at least two of these minerals, whereby said hydrotreatmentstage operates at a temperature of between 200 and 450° C., preferablybetween 220 and 350° C., in a preferred manner between 220 and 320° C.,and in an even more preferred manner between 220 and 310° C. Thepressure is between 1 MPa and 10 MPa, in a preferred manner between 1MPa and 6 MPa, and in an even more preferred manner between 1 MPa and 4MPa. The hourly volumetric flow rate is between 0.1 h−1 and 10 h−1. Thefeedstock is brought into contact with the catalyst in the presence ofhydrogen. The total quantity of hydrogen mixed with the feedstock issuch that the hydrogen/feedstock ratio is between 70 and 1,000 Nm3 ofhydrogen/m3 of feedstock, and in a preferred manner between 150 and 750Nm3 of hydrogen/m3 of feedstock.

In stage a) of the process according to the invention, the substrate ofthe catalyst that is implemented can also advantageously contain othercompounds and, for example, oxides that are selected from the group thatis formed by boron oxide, zirconia, titanium oxide, and phosphoricanhydride. The preferred substrate is an alumina substrate and in a verypreferred manner η-, δ-, or γ-alumina.

Said catalyst is advantageously a catalyst that comprises metals ofgroup VIII that are preferably selected from among nickel and cobalt,taken by itself or in a mixture, preferably combined with at least onemetal of group VIB, preferably selected from among molybdenum andtungsten, taken by itself or in a mixture.

The content of metal oxides of group VIII and preferably of nickel oxideis advantageously between 0.5 and 10% by weight of nickel oxide (NiO)and preferably between 1 and 5% by weight of nickel oxide, and thecontent of metal oxides of group VIB and preferably of molybdenumtrioxide is advantageously between 1 and 30% by weight of molybdenumoxide (MoO₃), preferably 5 to 25% by weight, the percentages beingexpressed in terms of % by weight relative to the total mass of thecatalyst.

The total content of oxides of metals of groups VIB and VIII in thecatalyst used in stage a) is advantageously between 5 and 40% by weightand preferably between 6 and 30% by weight relative to the total mass ofthe catalyst.

The ratio by weight that is expressed in terms of metal oxide betweenmetal (or metals) of group VIB to metal (or metals) of group VIII isadvantageously between 20 and 1 and in a preferred manner between 10 and2.

Said catalyst that is used in stage a) of the process according to theinvention is advantageously to be characterized by a stronghydrogenating power so as to orient as much as possible the selectivityof the reaction to a hydrogenation preserving the number of carbon atomsof the fatty chains, i.e., the hydrodeoxygenation method, so as tomaximize the yield of hydrocarbons entering the field of distillation ofkerosenes and/or gas oils. This is why the operation is performed in apreferred manner at a relatively low temperature. Maximizing thehydrogenating function also makes it possible to limit the reactions ofpolymerization and/or condensation leading to the formation of coke thatwould degrade the stability of the catalytic performances. Preferably, acatalyst of Ni or NiMo type is used.

Said catalyst that is used in stage a) for hydrotreatment of the processaccording to the invention can also advantageously contain a dopingelement that is selected from among phosphorus and boron, taken bythemselves or in a mixture. Said doping element can be introduced intothe matrix or preferably be deposited on the substrate. It is alsopossible to deposit silicon on the substrate by itself or withphosphorus and/or boron and/or fluorine.

The content by weight of oxide of said doping element is advantageouslyless than 20% and preferably less than 10%, and it is advantageously atleast 0.001%.

The metals of the catalysts that are used in stage a) for hydrotreatmentof the process according to the invention are sulfurized metals or metalphases and preferably sulfurized metals.

The scope of this invention would not be exceeded by using a singlecatalyst or several different catalysts simultaneously or successivelyin stage a) of the process according to the invention. This stage can becarried out industrially in one or more reactors with one or morecatalytic beds and preferably with liquid downflow.

According to stage b) of the process according to the invention, thehydrotreated effluent that is obtained from stage a) is subjected atleast partially, and preferably completely, to one or more separations.The object of this stage is to separate the gases from the liquid and inparticular to recover the hydrogen-rich gases that can also containgases such as CO and CO₂, and at least one liquid hydrocarbon base witha sulfur content that is less than 10 ppm by weight. The separation iscarried out according to all separation methods that are known to oneskilled in the art. The separation stage can advantageously beimplemented by any method that is known to one skilled in the art, suchas, for example, the combination of one or more high- and/orlow-pressure separators, and/or distillation stages and/or high- and/orlow-pressure stripping stages.

The water that is optionally formed during the stage a) forhydrotreatment of the process according to the invention can alsoadvantageously be separated at least partially from the liquidhydrocarbon base. The separation stage b) can therefore advantageouslybe followed by an optional stage for elimination of at least a portionof the water and preferably all of the water.

The optional stage for water removal has as its object to eliminate atleast partially the water that is produced during hydrotreatmentreactions. Elimination of water is defined as the elimination of thewater that is produced by hydrodeoxygenation (HDO) reactions. The moreor less complete elimination of the water can be based on the toleranceto water of the hydroisomerization catalyst used in the subsequent stagec) of the process according to the invention. The elimination of thewater can be carried out by any of the methods and techniques known toone skilled in the art, for example by drying, running it over adesiccant, flash, decanting, . . . .

According to stage c) of the process according to the invention, atleast a portion and preferably all of the liquid hydrocarbon baseobtained at the end of stage b) of the process according to theinvention is hydroisomerized in the presence of a fixed-bedhydroisomerization catalyst, whereby said catalyst comprises at leastone hydro-dehydrogenating metal that is selected from the group that isformed by the metals of group VIB and of group VIII of the periodictable, taken by itself or in a mixture, and a substrate that comprisesat least one zeolite that has at least one series of channels whoseopening is defined by a ring with 8 oxygen atoms, whereby said zeoliteis modified according to a particular process.

The Hydrogenating Phase

According to the invention, the catalyst that is implemented in stage c)for hydroisomerization of the process according to the inventioncomprises at least one hydro-dehydrogenating metal that is selected fromthe group that is formed by the metals of group VIII and the metals ofgroup VIB, taken by themselves or in a mixture.

Preferably, the elements of group VIII are selected from among iron,cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium, orplatinum, taken by themselves or in a mixture.

In the case where the elements of group VIII are selected from among thenoble metals of group VIII, the elements of group VIII areadvantageously selected from among platinum and palladium, taken bythemselves or in a mixture.

In the case where the elements of group VIII are selected from among thenon-noble metals of group VIII, the elements of group VIII areadvantageously selected from among iron, cobalt and nickel, taken bythemselves or in a mixture.

Preferably, the elements of group VIB of the catalyst according to thisinvention are selected from among tungsten and molybdenum.

In the case where the catalyst comprises at least one metal of group VIBin combination with at least one non-noble metal of group VIII, themetal content of group VIB is advantageously encompassed, in oxideequivalent, between 5 and 40% by weight relative to the total mass ofsaid catalyst, in a preferred manner between 10 and 35% by weight and ina very preferred manner between 15 and 30% by weight, and the content ofnon-noble metal of group VIII is advantageously encompassed, in oxideequivalent, between 0.5 and 10% by weight relative to the total mass ofsaid catalyst, in a preferred manner between 1 and 8% by weight, and ina very preferred manner between 1.5 and 6% by weight.

In the case where said catalyst comprises at least one metal of groupVIB in combination with at least one non-noble metal of group VIII, saidcatalyst can also advantageously comprise at least one doping elementthat is selected from the group that consists of silicon, boron, andphosphorus, taken by itself or in a mixture, whereby the content ofdoping element is preferably between 0 and 20% by weight of oxide of thedoping element, in a preferred manner between 0.1 and 15% by weight, ina very preferred manner between 0.1 and 10% by weight, and in a verypreferred manner between 0.5 and 6% by weight relative to the total massof the catalyst.

In the case where the hydrogenating function comprises an element ofgroup VIII and an element of group VIB, the following metal combinationsare preferred: nickel-molybdenum, cobalt-molybdenum, nickel-tungsten,cobalt-tungsten, and in a very preferred manner: nickel-molybdenum,cobalt-molybdenum, and nickel-tungsten. It is also possible to usecombinations of three metals, such as, for example,nickel-cobalt-molybdenum.

When a combination of metals of group VI and group VIII is used, thecatalyst is then preferably used in a sulfurized form.

When the hydro-dehydrogenating element is a noble metal of group VIII,the catalyst preferably contains a content of noble metal of between0.01 and 10% by weight, in an even more preferred manner 0.02 to 5% byweight relative to the total mass of said catalyst. The noble metal ispreferably used in its reduced and non-sulfurized form.

It is advantageously also possible to use a catalyst that is based onreduced and non-sulfurized nickel. In this case, the content of metal inits oxide form is advantageously between 0.5 and 25% by weight relativeto the finished catalyst. Preferably, the catalyst also contains, inaddition to the reduced nickel, a metal of group IB and preferablycopper, or a metal of group IVB and preferably tin in proportions suchthat the ratio by mass of the metal of group IB or IVB and nickel to thecatalyst is advantageously between 0.03 and 1.

Said hydroisomerization catalyst that is used in stage c) of the processaccording to the invention comprises a substrate that comprises at leastone modified zeolite and advantageously an oxide-type porous mineralmatrix, whereby said substrate comprises and preferably consists of,preferably:

-   -   0.1 to 99.8% by weight, preferably 0.1 to 80% by weight, and in        an even more preferred manner 0.1 to 70% by weight, and in a        very preferred manner 0.1 to 50% by weight of modified zeolite        according to the invention relative to the total mass of the        catalyst,    -   0.2 to 99.9% by weight, preferably 20 to 99.9%, in a preferred        manner 30 to 99.9% by weight, and in a very preferred manner 50        to 99.9% by weight relative to the total mass of catalyst, of at        least one oxide-type porous mineral matrix.

The Zeolite According to the Invention

According to the invention, the zeolite that is contained in thesubstrate of the catalyst that is used in stage c) of the processaccording to the invention comprises at least one series of channelswhose opening is defined by a ring with 8 oxygen atoms (8 MR) beforebeing modified. Said zeolite is selected from among the zeolites thatare defined in the classification “Atlas of Zeolite Structure Types,”Ch. Baerlocher, L. B. McCusker, D. H. Olson, 6^(th) Edition, Elsevier,2007, Elsevier” that has at least one series of channels whose openingof pores is defined by a ring that contains 8 oxygen atoms.

According to one particular embodiment, the initially used zeolite,before being modified, can advantageously contain—in addition to atleast one series of channels whose opening is defined by a ring with 8oxygen atoms (8 MR)—at least one series of channels whose pore openingis defined by a ring that contains 10 oxygen atoms (10 MR) and/or atleast one series of channels whose pore opening is defined by a ringthat contains 12 oxygen atoms (12 MR).

The zeolite can advantageously contain at least one other element T,different from silicon and aluminum, being integrated in tetrahedralform in the framework of the zeolite. Preferably, said element T isselected from among iron, germanium, boron and titanium and represents aproportion by weight of between 2 and 30% of all of the constituentatoms of the zeolitic framework other than the oxygen atoms. The zeolitethen has an atomic ratio (Si+T)/Al of between 2 and 200, preferablybetween 3 and 100, and in a very preferred manner between 4 and 80,whereby T is defined as above.

Preferably, the zeolite that is contained in the substrate of thecatalyst that is used in stage c) of the process according to theinvention is selected from among the zeolites Y, ZSM-48, ZBM-30, IZM-1and COK-7, taken by themselves or in a mixture. Preferably, the zeoliteis selected from among the zeolites Y, ZSM-48, ZBM-30, IZM-1 and COK-7,taken by themselves or in a mixture. Very preferably, said zeolite isselected from among the zeolites Y, ZSM-48 and ZBM-30, whereby ZBM 30 ispreferably synthesized with the organic structuranttriethylenetetramine, taken by themselves or in a mixture.

The ZBM-30 zeolite is described in the patent EP-A-46 504, and the COK-7zeolite is described in the patent application EP 1 702 888 A1 or FR 2882 744 A1.

The IZM-1 zeolite is described in the patent application FR-A-2 911 866,and the ZSM 48 zeolite is described in Schlenker, J. L.; Rohrbaugh, W.J.; Chu, P.; Valoyocsik, E. W.; and Kokotailo, G. T. Title: TheFramework Topology of ZSM-48: A High Silica Zeolite Reference: Zeolites,5, 355-358 (1985) Material *ZSM-48.”

In a more preferred manner, the initially used zeolite is an FAU zeolitethat has a three-dimensional network of channels whose opening isdefined by a ring with 12 oxygen atoms (12 MR), and in an even morepreferred manner, the initial zeolite is the Y zeolite.

Preferably, said zeolite can advantageously be dealuminified in all ofthe known manners by one skilled in the art such that the atomic ratioof silicon to aluminum of the zeolite is between 2.5 and 200, preferablybetween 3 and 100, and even more preferably between 4 and 80. The atomicratio of the silicon to aluminum Si/Al framework of the zeolite ismeasured by NMR of silicon and aluminum according to a method that isknown to one skilled in the art.

The FAU-structural-type zeolite that has undergone one or moredealuminification stages and that has a three-dimensional network ofchannels whose opening is defined by a ring with 12 oxygen atoms (12 MR)is suitable for the implementation of the catalyst that is used in theprocess according to the invention. Preferably, the initially usedzeolite is a dealuminified FAU zeolite, and in a very preferred manner,the initial zeolite is the dealuminified Y zeolite.

Process for Modification of the Zeolite that is Contained in theSubstrate of the Catalyst that is Used in the Process According to theInvention.

According to the invention, the zeolite that is contained in thesubstrate of the catalyst that is used in stage c) of the processaccording to the invention, initially exhibiting, before being modified,at least one series of channels whose opening is defined by a ring with8 oxygen atoms (8 MR), is modified by a′) a stage for introducing atleast one alkaline cation that belongs to group IA or IIA of theperiodic table, b′) a stage for treatment of said zeolite in thepresence of at least one molecular compound that contains at least onesilicon atom, c′) at least one partial exchange of alkaline cations byNH₄ ⁺ cations, and d) at least one heat treatment stage.

Said initial zeolite is therefore modified according to a modificationprocess that comprises at least one stage a′) for introducing at leastone alkaline cation that belongs to the groups IA and IIA of theperiodic table, whereby said cation(s) is/are preferably selected fromamong the cations Na⁺, Li⁺, K⁺, Rb⁺, Cs⁺, Ba²⁺ and Ca²⁺, and in a verypreferred manner, said cation is the Na⁺ cation. This stage can becarried out by any of the methods known to one skilled in the art, andpreferably this stage is carried out by the so-called ion-exchangemethod.

At the end of stage a′) of the modification process, the zeolite that iscontained in the substrate of the catalyst used in stage c) of theprocess according to the invention is found in cationic form.

The process for modification of said zeolite next comprises a stage b′)for treatment in the presence of at least one molecular compound thatcontains at least one silicon atom. This stage is called a stage forselecting said zeolite. In terms of this invention, “selecting” isdefined as the neutralization of the acidity of each of the crystals ofthe cationic zeolite. The neutralization of the acidity can be done byany method that is known to one skilled in the art. The conventionalmethods generally use molecular compounds that contain atoms that caninteract with the sites of the crystals of the zeolite. The molecularcompounds that are used within the scope of the invention are organic orinorganic molecular compounds that contain one or more silicon atom(s).

Also, according to treatment stage b′), the cationic zeolite that isprepared according to stage a′) is subjected to a treatment stage in thepresence of at least one molecular compound that contains at least onesilicon atom. Said stage b′) allows the deposition of a layer of saidmolecular compound that contains at least one silicon atom at thesurface of the crystals of the zeolite that will be transformed afterstage c′) into a layer of amorphous silica on the surface of each of thecrystals of the zeolite.

Preferably, the molecular compound that contains at least one siliconatom is selected from among the compounds of formulas Si—R₄ and Si₂—R₆,where R is selected from among hydrogen, an alkyl, aryl or acyl group,an alkoxy group (O—R′), a hydroxyl group (—OH), or a halogen, andpreferably an alkoxy group (O—R′). Within the same molecule Si—R₄ orSi₂—R₆, the group R can advantageously be either identical or different.Preferably, the molecular compound is selected from among the compoundsof formula Si₂H₆ or Si(C₂H₅)₃(CH₃). Thus, the molecular compound thatcontains at least one silicon atom that is used in stage b) of theprocess according to the invention can advantageously be a compound suchas silane, disilane, alkylsilane, alkoxysilane or siloxane.

Said molecular compound that is used for implementing stage b′)according to the invention preferably comprises at most two siliconatoms per molecule.

In a very preferred manner, said molecular compound has a compound ofgeneral formula Si—(OR′)₄ where R′ is an alkyl, aryl or acyl group,preferably an alkyl group, and very preferably an ethyl group.

Very preferably, the molecular compound that contains at least onesilicon atom is the molecular compound tetraethylorthosilicate (TEOS) offormula Si(OCH₂CH₃)₄.

Said stage b′) of the process for modification that consists in treatingthe cationic zeolite that is exchanged according to stage a′) in thepresence of at least one molecular compound that contains at least onesilicon atom is advantageously implemented by deposition of saidcompound on the inside and outside surfaces of the zeolite. It ispossible to initiate a gas-phase deposition called a CVD (“ChemicalVapor Deposition”) deposition or a liquid-phase deposition that iscalled a CLD (“Chemical Liquid Deposition”) deposition by any of themethods that are known to one skilled in the art. In a very preferredmanner, said stage b′) is implemented by initiating the deposition ofsaid molecular compound that contains at least one liquid-phase siliconatom.

If stage b′) of the modification process is implemented by gas-phasedeposition (CVD), it is advantageously implemented in a fixed-bedreactor. Prior to the gas-phase deposition reaction (CVD) in saidfixed-bed reactor, the zeolite is preferably activated. The activationof the zeolite in the fixed-bed reactor is implemented under oxygen, inair, or under a cover gas, or under a mixture of air and cover gas oroxygen and cover gas. The temperature for activating the zeolite isadvantageously between 100 and 600° C. and very advantageously between300 and 550° C. The molecular compound that contains at least onesilicon atom that should be deposited on the outside surface of each ofthe crystals of the zeolite is sent into the vapor-phase reactor,whereby said molecular compound is diluted in a carrier gas that can beeither hydrogen (H₂), or air, or argon (Ar), or helium (He), or elsenitrogen (N₂); preferably, the carrier gas is a cover gas that isselected from among Ar, He and N₂. Said molecular compound that containsat least one silicon atom is deposited on the outside surface of saidvapor-phase zeolite. To obtain a layer of amorphous silica of optimalquality on the outside surface of the zeolite at the end of stage c′),it is necessary to select the operating conditions properly for thedeposition of the molecular compound that contains at least one siliconatom. In particular, the temperature of the zeolite bed during thedeposition is preferably between 10 and 300° C., and very preferablybetween 50 and 200° C.; the partial pressure, in the gas phase, of themolecular compound to be deposited on the outside surface of the zeoliteis preferably between 0.001 and 0.5 bar, and very preferably between0.01 and 0.2 bar; the duration of the deposition is preferably between10 minutes and 10 hours, and very preferably between 30 minutes and 5hours, and even more preferably between 1 and 3 hours.

If stage b′) of the modification process is carried out by liquid-phasedeposition (CLD), it is advantageously carried out while being stirred.A CLD-phase deposition can be done either in aqueous medium or in anorganic solvent. During impregnation in an aqueous medium of themolecular compound that contains at least one silicon atom, it may ormay not be possible to add one or more surfactant(s) into theimpregnation solution. The CLD deposition is well known to one skilledin the art (Chon et al., Studies in Surface Science and Catalysis, Vol.105, 2059-2065, 1997). In a preferred manner, said molecular compoundthat contains at least one silicon atom is deposited on the outsidesurface of said zeolite in an anhydrous organic solvent. The organicsolvent is advantageously selected from among the saturated orunsaturated molecules containing 5 to 10 carbon atoms, and in apreferred manner 6 to 8 carbon atoms. To obtain a layer of amorphoussilica of optimal quality on the outside surface of the zeolite at theend of stage c′), it is necessary to select the operating conditionsproperly for the deposition of the molecular compound that contains atleast one silicon atom. In particular, the temperature of the organicsolvent solution is preferably between 10 and 100° C., and verypreferably between 30 and 90° C. The quantity of silica added to thesolution of anhydrous solvent is advantageously between 0.0001 and 5% byweight, preferably between 0.0001 and 2% by weight, and in an even morepreferred manner between 0.0005 and 1% by weight relative to thequantity of zeolite. The duration of the deposition is preferablybetween 5 minutes and 10 hours, preferably between 30 minutes and 5hours, and even more preferably between 1 and 3 hours.

The process for modification of the zeolite next comprises a stage c′)that corresponds to at least one partial exchange of alkaline cationsthat belong to the groups IA and IIA of the periodic table introducedduring stage a′) and preferably Na⁺ cations by NH₄ ⁺ cations. Partialexchange of alkaline cations, and preferably Na⁺ cations by NH₄ ⁺cations, is defined as the exchange of 80 to 99%, in a preferred manner85 to 98%, and in a more preferred manner 90 to 98% of the alkalinecations and preferably Na+ cations by NH4+ cations. The quantity ofalkaline cations remaining and preferably the quantity of Na+ cationsremaining in the modified zeolite, relative to the quantity of NH4+cations initially present in the zeolite, is advantageously between 1and 20%, preferably between 1.5 and 20%, in a preferred manner between 2and 15%, and in a more preferred manner between 2 and 10%.

Preferably, for this stage, several ion exchange(s) are initiated with asolution that contains at least one ammonium salt that is selected fromamong the salts of chlorate, sulfate, nitrate, phosphate or acetate ofammonium, in such a way as to eliminate, at least partially, thealkaline cations and preferably the Na⁺ cations that are present in thezeolite. Preferably, the ammonium salt is ammonium nitrate NH₄NO₃.

Thus, preferably, the content of alkaline cations remaining andpreferably Na⁺ cations in the modified zeolite at the end of stage c′)is preferably such that the alkaline cation/aluminum molar ratio andpreferably the Na/Al molar ratio is between 0.2:1 and 0.01:1, preferablybetween 0.2:1 and 0.015:1, in a more preferred manner between 0.15:1 and0.02:1, and in an even more preferred manner between 0.1:1 and 0.02:1.

The desired Na/Al ratio is obtained by adjusting the NH4+ concentrationof the cationic exchange solution, the temperature of the cationicexchange, and the cationic exchange number. The concentration of theNH4+ solution in the solution advantageously varies between 0.01 and 12mol/L, and preferably between 1 and 10 mol/L. The temperature of theexchange stage is advantageously between 20 and 100° C., preferablybetween 60 and 95° C., in a preferred manner between 60 and 90° C., andin a more preferred manner between 60 and 85° C., and in an even morepreferred manner between 60 and 80° C. The cationic exchange numberadvantageously varies between 1 and 10 and preferably between 1 and 4.

Maintaining a controlled content of alkaline cations and preferably Na+cations instead of protons makes it possible to neutralize the mostacidic Brønsted and Lewis sites of the zeolite, which reduces thesecondary cracking of the molecules of gasoline middle distillatesduring the hydrocracking reactions. This result makes it possible toobtain a gain in selectivity of middle distillates. If the quantity ofalkaline cations and preferably of Na+ cations remaining in thestructure of the modified zeolite is too large, the number of Brønstedacid sites decreases too greatly, which produces a loss of activity ofthe catalyst.

The process for modification of the zeolite next comprises at least oneheat treatment stage d′). This heat treatment makes possible both thedecomposition of the molecular compound that contains at least onesilicon atom deposited on the zeolite at the end of stage b′), and thetransformation of the NH₄ ⁺ cations, partially exchanged at the end ofstage c′), into protons. The heat treatment according to the inventionis carried out at a temperature that is preferably between 200 and 700°C., more preferably between 300 and 500° C. Said heat treatment stage isadvantageously implemented in air, under oxygen, under hydrogen, undernitrogen or under argon, or under a mixture of nitrogen and argon. Theduration of this treatment is advantageously between 1 and 5 hours. Atthe end of said heat treatment stage d′), a layer of amorphous silica isdeposited on the surface of each of the crystals of the zeolite, and theprotons of the zeolite are partially regenerated.

The Amorphous or Poorly Crystallized Oxide-Type Porous Mineral Matrix

The substrate of the hydroisomerization catalyst that is used in stagec) of the process according to the invention advantageously contains aporous mineral matrix, preferably amorphous, which advantageouslyconsists of at least one refractory oxide. Said matrix is advantageouslyselected from the group that is formed by alumina, silica, clays,titanium oxide, boron oxide, and zirconia. The matrix can consist of amixture of at least two of the oxides cited above, and preferablysilica-alumina. It is also possible to select the aluminates. It ispreferred to use matrices that contain alumina in all of these formsthat are known to one skilled in the art, for example gamma-alumina.

It is also advantageously possible to use mixtures of alumina andsilica, and mixtures of alumina and silica-alumina.

Preparation of the Catalyst

The modified zeolite can be, without this being limiting, for example,in the form of powder, ground powder, suspension, and a suspension thathas undergone a deagglomeration treatment. Thus, for example, themodified zeolite can advantageously be put into a suspension that may ormay not be slightly acidic at a concentration that is adjusted to thefinal zeolite content that is targeted in the substrate. Thissuspension, commonly called a slip, is then advantageously mixed withthe precursors of the matrix.

According to a preferred preparation method, the modified zeolite canadvantageously be introduced during the shaping of the substrate withthe elements that constitute the matrix. For example, according to thispreferred method of this invention, the modified zeolite according tothe invention is added to a moist alumina gel during the stage forshaping the substrate.

One of the preferred methods of the shaping of the substrate in thisinvention consists in kneading at least one modified zeolite with amoist alumina gel for several tens of minutes, and then in passing thethus obtained paste through a die for forming extrudates with a diameterof between 0.4 and 4 mm.

According to another preferred preparation method, the modified zeolitecan be introduced during the synthesis of the matrix. For example,according to this preferred method of this invention, the modifiedzeolite is added during the synthesis of the silico-aluminum matrix; thezeolite can be added to a mixture that consists of an alumina compoundin an acidic medium with a completely soluble silica compound.

The substrate can be shaped by any technique that is known to oneskilled in the art. The shaping can be carried out, for example, byextrusion, by pelletizing, by the drop (oil-drop) coagulation method, byturntable granulation or by any other method that is well known to oneskilled in the art.

At least one calcination cycle can be carried out after any of thestages of the preparation. The calcination treatment is usually carriedout in air at a temperature of at least 150° C., preferably at least300° C., and in a more preferred manner between about 350 and 1,000° C.

The elements of group VIII and/or the elements of group VIB, optionallyat least one doping element that is selected from among boron, silicon,and phosphorus, and optionally the elements of groups IVB and IB in thecase of a catalyst with a reduced nickel base, optionally can beintroduced, completely or partially, at any stage of the preparation,during the synthesis of the matrix, preferably during the shaping of thesubstrate, or in a very preferred manner after the shaping of thesubstrate by any method that is known to one skilled in the art. Theycan be introduced after the shaping of the substrate and after or beforethe drying and the calcination of the substrate.

According to a preferred method of this invention, all or part of theelements of group VIII and/or the elements of group VIB, optionally atleast one doping element that is selected from among boron, silicon andphosphorus, and optionally the elements of groups IVB and IB in the caseof a catalyst with a reduced nickel base can be introduced during theshaping of the substrate, for example during the stage for kneading themodified zeolite with a moist alumina gel.

According to another preferred method of this invention, all or part ofthe elements of the group VIII, optionally at least one doping elementthat is selected from among boron, silicon, and phosphorus, andoptionally the elements of groups IVB and IB in the case of a catalystwith a reduced nickel base can be introduced by one or more operationsfor impregnation of the substrate that is shaped and calcined by asolution that contains the precursors of these elements. In a preferredway, the substrate is impregnated by an aqueous solution. Theimpregnation of the substrate is preferably carried out by the so-called“dry” impregnation method that is well known to one skilled in the art.

The following doping elements: boron and/or silicon and/or phosphoruscan be introduced into the catalyst at any level of the preparation andaccording to any technique that is known to one skilled in the art.

In the case where the catalyst of this invention contains at least onemetal of group VIII, the metals of group VIII are preferably introducedby one or more operations for impregnation of the substrate that isshaped and calcined, and after those of group VIB or at the same time asthe latter, in the case where said catalyst contains at least one metalof group VIII combined with at least one metal of group VIB.

For example, among the sources of molybdenum and tungsten, it ispossible to use oxides and hydroxides, the molybdic and tungstic acidsand their salts, in particular ammonium salts such as ammoniummolybdate, ammonium heptamolybdate, ammonium tungstate, phosphomolybdicacid, phosphotungstic acid, and salts thereof, silicomolybdic acid,silicotungstic acid, and salts thereof. The oxides and salts of ammoniumsuch as the ammonium molybdate, ammonium heptamolybdate, and ammoniumtungstate are preferably used.

The sources of non-noble elements of group VIII that can be used arewell known to one skilled in the art. For example, for the non-noblemetals, nitrates, sulfates, hydroxides, phosphates, halides such as, forexample, chlorides, bromides and fluorides, and carboxylates, such as,for example, acetates and carbonates, will be used.

The sources of noble elements of group VIII that can advantageously beused are well known to one skilled in the art. For the noble metals,halides, for example, chlorides, nitrates, acids such ashexachloroplatinic acid, hydroxides, and oxychlorides such as ammoniacalruthenium oxychloride, are used. It is also possible advantageously touse the cationic complexes such as the ammonium salts when it is desiredto deposit the metal on the Y-type zeolite by cationic exchange.

The noble metals of group VIII of the catalyst of this invention canadvantageously be present completely or partially in metallic and/oroxide form.

The promoter element(s) selected from the group that is formed bysilicon, boron and phosphorus can advantageously be introduced by one ormore impregnation operations with excess solution on the calcinedprecursor.

The boron source can advantageously be boric acid, preferably orthoboricacid H3BO3, ammonium biborate or pentaborate, boron oxide, and boricesters. Boron can be introduced, for example, in the form of a mixtureof boric acid, hydrogen peroxide, and a basic organic compound thatcontains nitrogen, such as ammonia, primary and secondary amines, cyclicamines, compounds of the family of pyridine, and quinolines, and thecompounds of the pyrrole family Boron can be introduced by, for example,a boric acid solution in a water/alcohol mixture. The preferredphosphorus source is the orthophosphoric acid H3PO4, but its salts andesters, such as the ammonium phosphates, are also suitable. Phosphoruscan be introduced, for example, in the form of a mixture of phosphoricacid and a basic organic compound that contains nitrogen, such asammonia, primary and secondary amines, cyclic amines, compounds of thepyridine family, and quinolines and compounds of the pyrrole family.

Numerous silicon sources can advantageously be used. Thus, it ispossible to use ethyl orthosilicate Si(OEt)4, siloxanes, polysiloxanes,silicones, silcone emulsions, halide silicates such as the ammoniumfluorosilicate (NH4)2SiF6 or sodium fluorosilicate Na2SiF6. Thesilicomolybdic acid and its salts, and the silicotungstic acid and itssalts can also advantageously be used. Silicon can advantageously beadded by, for example, impregnation of ethyl silicate in solution in awater/alcohol mixture. The silicon can be added by, for example,impregnation of a silicone-type silicon compound or the silicic acidsuspended in water.

The element sources of group IB that can be used are well known to oneskilled in the art. For example, among the copper sources, it ispossible to use copper nitrate Cu(NO₃)₂.

The element sources of group IVB that can be used are well known to oneskilled in the art. For example, among tin sources, it is possible touse tin chloride SnCl₂.

The catalysts that are used in the process according to the inventionadvantageously have the shapes of spheres or extrudates. It isadvantageous, however, that the catalyst comes in the form of extrudateswith a diameter of between 0.5 and 5 mm and more particularly between0.7 and 2.5 mm The shapes are cylindrical (which can be hollow or not),braided cylindrical, multilobe (2, 3, 4 or 5 lobes, for example), rings.The cylindrical shape is used in a preferred manner, but any other shapecan be used. The catalysts according to the invention optionally can bemanufactured and used in the form of crushed powder, tablets, rings,balls, and wheels.

According to the invention, the metals of group VIB and/or of group VIIIof said catalyst are present in sulfur form, the sulfurization treatmentbeing described below.

In the case where the hydroisomerization catalyst contains at least onenoble metal, the noble metal that is contained in saidhydroisomerization catalyst is advantageously to be reduced. One of thepreferred methods for conducting the reduction of metal is the treatmentunder hydrogen at a temperature of between 150° C. and 650° C. and atotal pressure of between 1 and 250 bar. For example, a reductionconsists of a stage at 150° C. of two hours and then an increase intemperature up to 450° C. at the rate of 1° C./minute, and then a stageof two hours at 450° C.; during this entire reduction stage, the flowrate of hydrogen is 1,000 normal m³ of hydrogen/m³ of catalyst, and thetotal pressure is kept constant at 1 bar. The entire ex-situ reductionmethod can advantageously be taken into consideration.

According to stage c) for hydroisomerization of the process according tothe invention, at least one portion of the hydrocarbon base that isobtained from stage b) is brought into contact, in the presence ofhydrogen, with said hydroisomerization catalyst, at temperatures andoperating pressures that advantageously make it possible to carry outhydroisomerization of the non-converting feedstock. This means that thehydroisomerization is performed with a conversion of the 150° C.+fraction into the 150° C. fraction that is less than 20% by weight, in apreferred manner less than 10% by weight, and in a very preferred mannerless than 5% by weight.

Thus, according to the invention, the hydroisomerization stage c) of theprocess according to the invention is performed at a temperature ofbetween 150 and 500° C., preferably between 150° C. and 450° C., and ina very preferred manner between 200 and 450° C., at a pressure ofbetween 1 MPa and 10 MPa, preferably between 2 MPa and 10 MPa, and in avery preferred manner between 1 MPa and 9 MPa, at an hourly volumetricflow rate that is advantageously between 0.1 h⁻¹ and 10 h⁻, preferablybetween 0.2 and 7 h⁻¹, and in a very preferred manner between 0.5 and 5h⁻¹, at a flow rate of hydrogen such that the hydrogen/hydrocarbonvolumetric ratio is advantageously between 70 and 1,000 Nm³/m³ offeedstock, between 100 and 1,000 normal m³ of hydrogen per m³ offeedstock, and in a preferred manner between 150 and 1,000 normal m³ ofhydrogen per m³ of feedstock.

In a preferred manner, the optional hydroisomerization stage operates inco-current.

Techniques of Characterization

The quantity of alkaline cation that belongs to group IA or IIA of theperiodic table, and preferably the quantity of alkaline cation Na⁺remaining in the modified zeolite after the modification treatmentdescribed above, is measured by atomic adsorption according to a methodthat is known to one skilled in the art.

The Lewis and Brønsted acidity of zeolites is measured by adsorption ofpyridine followed by infra-red spectroscopy (FTIR). The integration ofthe characteristic bands of the pyridine coordinated at 1,455 cm⁻¹ andprotonated pyridine at 1,545 cm⁻¹ makes it possible to compare therelative acidity of the catalysts of the Lewis and Brønsted types,respectively. Before adsorption of the pyridine, the zeolite ispretreated under secondary vacuum at 450° C. for 10 hours with anintermediate stage at 150° C. for 1 hour. The pyridine is next adsorbedat 150° C. and then desorbed under secondary vacuum at this sametemperature before the spectra are taken.

The products, gas oil- and kerosene-based, obtained according to theprocess of the invention, are endowed with excellent characteristics.

The gas oil base that is obtained is of excellent quality:

-   -   Its sulfur content is less than 10 ppm by weight.    -   Its total aromatic compound content is less than 5% by weight,        and the polyaromatic compound content is less than 2% by weight.    -   The cetane number is excellent, higher than 55.    -   The density is less than 840 kg/m³, and most often less than 820        kg/m³.    -   Its kinematic viscosity at 40° C. is 2 to 8 mm²/s.    -   Its cold strength properties are compatible with the standards        in force, with a filterability boundary temperature at −15° C.        and a cloud point that is less than −5° C.

The kerosene that is obtained has the following characteristics:

-   -   A density of between 775 and 840 kg/m³    -   A viscosity at −20° C. less than 8 mm²/s    -   A crystal disappearance point of below −47° C.    -   A flash point of more than 38° C.    -   A smoke point of more than 25 mm

EXAMPLES Stage a): Hydrotreatment

170 g/h of pre-refined canola oil with a density of 920 kg/m³⁺ that hasa sulfur content of less than 10 ppm by weight, with a cetane number of35, and whose composition is presented in detail below, is introducedinto a reactor that is temperature-regulated in such a way as to ensurean isothermal operation and that has a fixed bed charged with 190 ml ofhydrotreatment catalyst based on nickel and molybdenum, having a nickeloxide content that is equal to 3% by weight, and a molybdenum oxidecontent that is equal to 16% by weight and a P₂O₅ content that is equalto 6%, whereby the catalyst is sulfurized in advance:

Fatty Acid Glycerides Nature of the Fatty Chain % by Mass Palmitic C16:04 Palmitoleic C16:1 <0.5 Stearic C18:0 2 Oleic C18:1 61 Linoleic C18:220 Linoleic C18:3 9 Arachidic C20:0 <0.5 Gadoleic C20:1 1 Behenic C22:0<0.5 Erucic C22:1 <1

700 Nm³ of hydrogen/m³ of feedstock is introduced into the reactor thatis kept at a temperature of 300° C. and at a pressure of 5 MPa.

Stage b): Separation of the Effluent that is Obtained from Stage a).

The entire hydrotreated effluent that is obtained from stage a) isseparated so as to recover the hydrogen-rich gases and a hydrocarbonbase.

Stage c): Hydroisomerization of the Hydrotreated Effluent that isObtained from Stage b) on a Catalyst According to the Invention

Preparation of the Modified Zeolite Used in the Catalyst According tothe Invention.

100 g of dealuminified HY zeolites, with an Si/Al framework ratio thatis equal to 11.5 and measured by NMR of silicon and aluminum, isexchanged by an NaNO₃ solution to obtain the NaY cationic form of the Yzeolite. The exchange is carried out in a flask that contains 1 L ofNallo₃ solution at 80° C. for 2 hours, and then the suspension isfiltered, and the zeolite is dried at 120° C. for one night. The NaYzeolite that is obtained is poured into a three-neck flask that contains1 L of anhydrous toluene and is equipped with a coolant. After anincrease in temperature to 60° C., the quantity of molecular compoundtetraethylorthosilicate TEOS corresponding to 1% by weight of silica isslowly introduced into the zeolite suspension by using a syringe pump.After stirring for 1 hour, the suspension is filtered, and the zeoliteis dried at 120° C. for one night. The modified zeolite is thenexchanged 3 times by a 1N solution of NH₄NO₃ to obtain the partiallyexchanged NH₄ ⁺ form, whereby the exchange is carried out at atemperature of 80° C. The decomposition of the TEOS and thetransformation of NH₄ ⁺ cations into protons is done under H₂O-saturatedN₂ at 350° C. for 2 hours, and then a heat treatment under pure N₂ isdone at 450° C. for 2 hours. The characterizations of the zeolites thatare measured by atomic adsorption spectroscopy and adsorption ofpyridine followed by infrared are provided in Table 1.

TABLE 1 Characterization of the Samples. Modified Y Anomalous Exchanged3 Times Unmodified (According to HY the Invention) Na/Al 0.001 0.05Quantity of Na⁺ remaining relative 0.1 5.0 to the quantity of NH₄ ⁺ thatwas initially present (%) Brønsted acid sites (i.a., 1545 cm⁻¹ 5.5 5.0band) after desorption of pyridine at 150° C. Lewis acid sites (i.a.,1455 cm⁻¹ 3.7 1.5 band) after desorption of pyridine at 150° C.

An unmodified HY zeolite that is not in accordance with the invention iscalled a dealuminified HY zeolite that is exchanged by an NH4NO3solution to obtain the cationic form of the Y zeolite but that has notbeen modified according to the modification process that is describedaccording to the invention.

The analytical results show that the quantity of Brønsted acid sitesslightly decreases and that the quantity of Lewis acid sites greatlydecreases on the modified zeolites. This acidity variation varies ininverse proportion to the quantity of sodium present in the samples.

Preparation of the Catalysts

The catalyst substrates according to the invention containing zeolitesthat may or may not be modified are produced by using 19.5 g of zeolitemixed with 80.5 g of a matrix that consists of ultrafine tabularboehmite or alumina gel marketed under the name SB3 by the Condéa ChemieGmbH Company. This powder mixture is then mixed with an aqueous solutionthat contains nitric acid at 66% by weight (7% by weight of acid pergram of dry gel), and then kneaded for 15 minutes. The kneaded paste isthen extruded through a die with a 1.2 mm diameter. The extrudates arenext calcined at 500° C. for 2 hours in air.

The thus prepared substrate extrudates are impregnated in the dry stateby a solution of a mixture of ammonium heptamolybdate and nickel nitrateand calcined in air at 550° C. in situ in the reactor. The contents byweight of oxides of the catalysts that are obtained are indicated inTable 2.

TABLE 2 Characteristics of the Catalysts. Modified Y Exchanged 3 TimesUnmodified According to Catalyst-Based Zeolite HY the Invention MoO₃ (%by weight) 12.1 12.4 NiO (% by weight) 3.2 3.1 Overall SiO₂ (% byweight) 14.7 14.1 Make-up to 100% (for the most part 70.0 70.4 composedof Al₂O₃ (% by weight)

The hydrotreated hydrocarbon effluent that is obtained at the end ofstage b) is hydroisomerized with hydrogen that is lost in ahydroisomerization reactor under the operating conditions below:

-   -   VVH (volume of feedstock/volume of catalyst/hour)=1 h⁻¹    -   Total working pressure: 5 MPa    -   Temperature: 300° C.    -   Hydrogen/Feedstock ratio: 700 normal liters/liter

The reaction temperature is set so as to achieve a gross conversion(denoted CB) that is equal to 70% by weight.

50 ppm by weight of dimethyl disulfide is added to the feedstock so asto simulate the partial pressures of H₂S and to keep the catalyst insulfide form. The thus prepared feedstock is injected into thehydroisomerization test unit that comprises a fixed-bed reactor withupward circulation of the feedstock (“up-flow”) into which 100 ml ofcatalyst is introduced. The catalyst is sulfurized by a directdistillation gas oil/DMDS and aniline mixture up to 320° C. Note thatany in-situ or ex-situ sulfurization method is suitable. Once thesulfurization is carried out, the feedstock can be transformed. Theoperating conditions of the test unit are indicated above.

The jet fuel yield (kerosene, 150-250° C. fraction, Kero yieldhereinafter) is equal to the percentage by weight of compounds that havea boiling point of between 150 and 250° C. in the effluents. The gas oilyield (250° C.+fraction) is equal to the percentage by weight ofcompounds that have a boiling point that is greater than 250° C. in theeffluents.

The temperature of 300° C. is adjusted so as to have a conversion of the150° C.⁺ fraction into the 150° C. fraction that is less than 5% byweight during the hydroisomerization in the case where thehydroisomerization catalyst that is used in stage c) of the processaccording to the invention contains the modified zeolite according tothe invention. In Table 3, we recorded the temperature of the yields inkerosene and gas oil for the catalysts described in the examples above.

TABLE 3 Catalytic Activities of the Hydroisomerization Catalysts. 150°C.- Kerosene Yield Gas Oil Yield Yield (% by Weight) (% by Weight)Unmodified HY 13 30 57 Modified Y, Exchanged 5 33 62 3 Times (Accordingto the Invention)

At a temperature of 300° C., the process that implements a catalystcontaining an unmodified zeolite entrains the production of a 150° C.−light fraction with a yield of 13% and therefore the production ofmiddle distillates with a yield that is lower relative to theimplementation of a catalyst that contains a modified zeolite accordingto the invention. The process according to the invention thereforedemonstrates that the catalyst that contains a modified zeoliteaccording to the invention and that is used in said process according tothe invention is more active than the anomalous catalysts for obtaininga level of conversion of the 150° C.+ fraction that is less than 5% byweight, while making it possible to obtain higher middle distillateyields, and therefore a better selectivity of middle distillates,relative to a hydroisomerization process that implements an anomalouscatalyst that contains an unmodified zeolite or a zeolite that ismodified in a manner that is not in accordance with the invention.

Without further elaboration, it is believed that one skilled in the artcan, using the preceding description, utilize the present invention toits fullest extent. The following preferred specific embodiments are,therefore, to be construed as merely illustrative, and not limitative ofthe remainder of the disclosure in any way whatsoever.

The entire disclosure of all applications, patents and publications,cited herein and of corresponding French application No. 06/04.910,filed Oct. 13, 2009 are incorporated by reference herein.

From the foregoing description, one skilled in the art can easilyascertain the essential characteristics of this invention and, withoutdeparting from the spirit and scope thereof, can make various changesand modifications of the invention to adapt it to various usages andconditions.

1. Process for treatment of feedstocks obtained from a renewable sourceand comprising the following stages: a) Hydrotreatment of said feedstockin the presence of a fixed-bed catalyst that comprises ahydro-dehydrogenating function comprising at least one metal of groupVIII and/or group VIB, taken by itself or in a mixture, and a substratethat is selected from the group that is formed by alumina, silica,silica-aluminas, magnesia, clays and mixtures of at least two of theseminerals, whereby said hydrotreatment stage operates at a temperature ofbetween 200 and 450° C., at a pressure of between 1 MPa and 10 MPa, atan hourly volumetric flow rate of between 0.1 h⁻¹ and 10 I⁻¹, and in thepresence of a total quantity of hydrogen mixed with the feedstock suchthat the hydrogen/feedstock ratio is between 70 and 1,000 Nm³ ofhydrogen/m³ of feedstock, b) Separation, starting from the effluent thatis obtained from stage a), of hydrogen, gases, and at least onehydrocarbon base, c) Hydroisomerization of at least a portion of saidhydrocarbon base that is obtained from stage b) in the presence of afixed-bed hydroisomerization catalyst, whereby said catalyst comprisesat least one hydro-dehydrogenating metal that is selected from the groupthat is formed by the metals of group VIB and group VIII of the periodictable and a substrate that comprises a zeolite that comprises at leastone series of channels whose opening is defined by a ring with 8 oxygenatoms, modified by a′) at least one stage for introducing at least onealkaline cation that belongs to group IA or IIA of the periodic table,b′) a stage for treatment of said zeolite in the presence of at leastone molecular compound that contains at least one silicon atom, c′) atleast one stage for partial exchange of said alkaline cations by NH₄ ⁺cations, and d′) at least one heat treatment stage, whereby saidhydroisomerization stage is carried out at a temperature of between 150and 500° C., at a pressure of between 1 MPa and 10 MPa, at an hourlyvolumetric flow rate of between 0.1 and 10 h⁻¹, and in the presence of atotal quantity of hydrogen mixed with the feedstock such that thehydrogen/feedstock ratio is between 70 and 1,000 Nm³/m³ of feedstock, d)Separation, starting from the effluent that is obtained from stage c),of hydrogen, gases, and at least one gas oil base and one kerosene base.2. Process according to claim 1, in which the element of group VIII isselected from among platinum and palladium, taken by themselves or in amixture.
 3. Process according to claim 2, in which said catalystcomprises, in % by weight relative to the total mass of the catalyst, acontent of noble metal of between 0.01 and 10% by weight.
 4. Processaccording to claim 1, in which the catalyst comprises at least one metalof group VIB in combination with at least one non-noble metal of groupVIII, whereby the metal content of group VIB encompasses, in oxideequivalent, between 5 and 40% by weight relative to the total mass ofsaid catalyst, and the content of non-noble metal of group VIIIencompasses, in oxide equivalent, between 0.5 and 10% by weight relativeto the total mass of said catalyst.
 5. Process according to claim 4, inwhich the non-noble element of group VIII is selected from among iron,cobalt and nickel, taken by themselves or in a mixture.
 6. Processaccording to claim 4, in which the element of group VIB is selected fromamong tungsten and molybdenum.
 7. Process according to claim 1, in whichthe zeolite that is contained in the substrate of the catalyst that isused in stage c) of the process according to the invention is selectedfrom among the zeolites Y, ZSM-48, ZBM-30, IZM-1 and COK-7, taken bythemselves or in a mixture.
 8. Process according to claim 7, in whichthe initially used zeolite is the Y zeolite.
 9. Process according toclaim 1, in which said alkaline cation that belongs to the groups IA andIIA introduced in stage a) is selected from among the cations Na+, Li+,K+, Rb+, Cs+, Ba2+ and Ca2+, and, preferably, said cation is the Na+cation.
 10. Process according to claim 1, in which the molecularcompound that contains at least one silicon atom that is used in thetreatment stage b) is selected from among the compounds of formula Si-R4and Si2-R6 where R is selected from among hydrogen, an alkyl, aryl oracyl group, an alkoxy group (O—R′), a hydroxyl group (—OH), or ahalogen.
 11. Process according to claim 1, in which the content ofalkaline cations remaining in the modified zeolite at the end of stagec) is such that the alkaline cation/aluminum molar ratio is between0.2:1 and 0.01:1.
 12. Process according to claim 11, in which thecontent of alkaline cations remaining in the modified zeolite at the endof stage c) is such that the alkaline cation/aluminum molar ratio isbetween 0.2:1 and 0.015:1.
 13. Process according to claim 11, in whichthe content of alkaline cations remaining in the modified zeolite at theend of stage c) is such that the alkaline cation/aluminum molar ratio isbetween 0.15:1 and 0.02:1.
 14. Process according to claim 1, in whichthe feedstocks that are obtained from renewable sources are selectedfrom among the oils and fats of plant or animal origin, or mixtures ofsuch feedstocks, containing triglycerides and/or free fatty acids and/oresters and said vegetable oils that can be raw or refined, totally orpartially, and obtained from the following plants: canola, sunflower,soybean, palm, palm-kernel, olive, coconut, jatropha, and the animalfats being selected from among lard or fats composed of waste from thefood industry or obtained from catering industries.